Fundamental Investigation of Fuel Transformations in Pulverized Coal Combustion and Gasification Technologies

Abstract

The goal of this project was to carry out the necessary experiments and analyses to extend current capabilities for modeling fuel transformations to the new conditions anticipated in next-generation coal-based, fuel-flexible combustion and gasification processes. This multi-organization, multi-investigator project has produced data, correlations, and submodels that extend present capabilities in pressure, temperature, and fuel type. The combined experimental and theoretical/computational results are documented in detail in Chapters 1-8 of this report, with Chapter 9 serving as a brief summary of the main conclusions. Chapters 1-3 deal with the effect of elevated pressure on devolatilization, char formation, and char properties. Chapters 4 and 5 deal with advanced combustion kinetic models needed to cover the extended ranges of pressure and temperature expected in next-generation furnaces. Chapter 6 deals with the extension of kinetic data to a variety of alternative solid fuels. Chapter 7 focuses on the kinetics of gasification (rather than combustion) at elevated pressure. Finally, Chapter 8 describes the integration, testing, and use of new fuel transformation submodels into a comprehensive CFD framework. Overall, the effects of elevated pressure, temperature, heating rate, and alternative fuel use are all complex and much more work could be further undertaken in this area. Nevertheless, the current project with its new data, correlations, and computer models provides a much improved basis for model-based design of next generation systems operating under these new conditions.

Experimental Study on the Micro-Structure of the Coal Char at High Heating Rate and Elevated Pressures

“…Simultaneously, the tendency of the specific surface area was the same over all. The values of the area had a different orders from that in the literature [7,8], which was conjectured due to the different de-tar method. Figure 11 (right) proved this point.…”

“…During gasification process, coal particles experiences up to 10 4 ~ 10 6 K/s heating rate, much higher than that in a thermal gravimetric analyzer or a fixed bed reactor. Research shows that the heating rate influences the physical structure and chemical reactivity of char greatly [4][5][6][7]. Therefore, in the experiment, high heating rate methods were used to prepare char.…”

“…Meanwhile, the large-scale gasification typically runs under high pressure conditions, so the study requires a pressurized system under laboratory conditions. Some scholars suggest that the morphology, pore structure of the resulting char under pressurized conditions was different from that under atmospheric conditions [7]. Researchers of Brigham Young University found that increased pressure will change the char morphology, lead to coal swelling ratio increasing, and decrease the number of micro pores and specific surface area of char [7].…”

“…Some scholars suggest that the morphology, pore structure of the resulting char under pressurized conditions was different from that under atmospheric conditions [7]. Researchers of Brigham Young University found that increased pressure will change the char morphology, lead to coal swelling ratio increasing, and decrease the number of micro pores and specific surface area of char [7]. Zeng et al discovered the resulting char reactivity reduced with increasing system pressure, which may be associated with a specific surface area of char [8].…”